Nanometer and micrometer sized hollow cubic metal oxides have found increasing applications in meta-materials, wave scattering, microelectronics, wave absorption, drug delivery, nano-sized devices, lightweight composites, disinfection, sensing, and catalysis. These applications require hollow dense spherical metal oxides or hollow dense cubic metal oxides to be chemically and/or mechanically stable.
Conventional fabrication methods include steps of sacrificial templating (e.g., using expensive templates), spray freezing, and microemulsion formation. Such fabrication methods include a high cost, tedious synthesis of hollow metal oxides, which however, lack of a good control of monodispersity, integrity, and mechanical reliability of the hollow structures. Applications of the conventionally formed hollow structures are then limited. Other conventional fabrication methods involve sputtering, chemical vapor deposition, electroplating coatings, and molecular beam epitaxy growth. These methods require high vacuum, high energy, and long process time.
Thus, there is a need to overcome these and other problems of the prior art and to provide methods of fabricating hollow cubes that are energy efficient, reliable, low cost, template-free, and nondestructive.